The tool and die industry deals with the manufacture and modification of mechanical elements and tools. One of the tools frequently utilized in the industry is a rotary grinding wheel. Rotary grinding wheels may be utilized as tools for shaping the exterior portions of various elements or for removing imperfections. However, they may also be used as a cutting element similar in some ways to a saw in that a grinding wheel may be used to grind a slot in a slab or a sheet of material. The present invention deals with this application of the tool.
A rotary grinding wheel is a quantity of abrasive material bonded together to form a regular symmetrical disk having a discrete thickness. The particular type of abrasive material, the binding material and the dimensions are all selected in accordance with the particular use to which the grinding wheel is to be put.
The present invention regards methods and devices for modifying the width of a grinding wheel and dressing it to a particular uniform width along a significant portion of its radius. In the past, this has been accomplished by rotating the grinding wheel rapidly while bringing one side of the wheel into contact with a point or edge of material which is harder and more abrasive than the material of the wheel. Since grinding wheels are typically constructed of carborundum or powdered diamond suspensions it is usually necessary that the abrasive edge or point be diamond, since the milling will only be possible with an agent harder than or of equal hardness to the wheel material.
One commonly used prior art method of dressing the size or width of the grinding wheel is to use a diamond point on one side of the wheel and a positioning element, such as a flat plate parallel to the plane of rotation of the wheel, on the other side. Typically, either the diamond point or the positioning plate is spring loaded such that the wheel is urged into the proper orientation but is not forced. After one side of the wheel has been properly dressed then the other side is treated in a similar manner. This method has been entirely adequate for use with grinding wheels of macroscopic widths and relatively large dimensional tolerances.
However, with the explosive development of industries regarding micro-miniature circuitry, there has arisen a concurrent need for grinding wheels having very narrow widths and very precise tolerances. It has been found that the prior art methods do not dress the wheels with sufficient accuracy for these applications. The prior art size dressing methods frequently lead to relevant differences in thicknesses along the radius of the wheel as well as occasional spiraling which may lead to resulting grinding wheels similar in shape to a warped phonograph record. Such results are unacceptable.
In response to the difficulties encountered in dressing very narrow grinding wheels, the art has responded with some very sophisticated and complex devices. These have included micrometer type spacing controls both on the positioning plate and on the diamond tip and various other means of precisely positioning the abrasive elements. These complex methods have been more successful at solving the problem than earlier efforts, but have been difficult and expensive to manufacture and require constant adjustment to maintain them in proper orientation. None of the prior art devices adequately solve the problems involved in grinding wheels for the electronics industry in a simple and easily manufactured and utilized manner.